Clamp for line-alternate signals

Abstract

A clamp for television signals, the sources of which alternate on a line recurrent basis includes a plurality of capacitors having a common terminal coupled to the sources of signal and a multiplexing switch for sequentially connecting one of the capacitors between its source and a clamp.

What is claimed is: 
     
       1. A clamp for television signals from a plurality of sources, comprising: a source of a first plurality of line-sequential television signals, each line including a recurrent identifiable portion;   a second plurality of coupling capacitors having a terminal in common, each coupling capacitor having a second terminal, said terminal in common being coupled to said source of television signals, said first and second pluralities being equal;   a source of reference voltage to which said recurrent identifiable portions of said television signals are to be clamped;   first controllable switch means including a controlled current path having first and second terminals and a control electrode, said first terminal of said controlled current path being coupled to said source of reference voltage;   second controllable switch means coupled to said second terminals of said coupling capacitors and to said second terminal of said controlled current path of said first controllable switch means;   first control means coupled to said second controllable switch means for coupling said source of television signals to said second terminal of said first switch means by sequential coupling of said second terminals of said coupling capacitors with said second terminal of said first switching means in timed relationship with the line-sequence of said source of television signals; and   second control means coupled to said control terminal of said first controllable switch means for rendering said controlled current path conductive during said recurrent identifiable portions of each horizontal line.   
     
     
       2. A clamp according to claim 1 wherein said identifiable portions are sync portions. 
     
     
       3. A clamp according to claim 1 wherein said identifiable portions are blanking levels. 
     
     
       4. A clamp for television signals having an identifiable portion at an extreme amplitude excursion of the signal, said signals being derived in regular recurrence from different sources, the clamp comprising: a plurality of coupling capacitors having a terminal in common, said common terminal being coupled to the source of television signals, said plurality being equal in number to the number of different sources from which said television signals are derived, each of said coupling capacitors also including a second terminal;   multiplex switch means coupled to said second terminals of said coupling capacitors and to an output terminal of said clamp for recurrently coupling each of said sources to said output terminal by way of one of said plurality of coupling capacitors;   a source of reference voltage; and   controllable switch means coupled to said source of reference voltage and to said output terminal for coupling said reference voltage source to said output terminal during the extreme amplitude excursion of each of said signals.   
     
     
       5. A clamp pursuant to claim 4 wherein said controllable switch means comprises a diode. 
     
     
       6. A clamp pursuant to claim 4 wherein said controllable switch means is keyed.